Don't you bring your peak flow meter with you to the doctor appointment?...Yes, peakflowmeters can vary greatly. To obtain an accurrate/consistant result you need to use the same peakflow meter. As the meter wears out it can either become sticky or to loose, so again, it is important to use the same meter if possible. My son has asthma and we check his peakflows AM and PM daily. We take his meter to the doctor's office and he blows levels with his and the doctor's so we can see how close the two meters are reading out.

Knowing where youir peakflows are at on a daily basis can often give you heads up. My son's numbers will often drop days before he starts wheezing or coughing. Sometimes it is a virus brewing, other times it has been exposure to an irratant. Those levels and numbers are a visible way to tell just how serious a problem is and head it off.

Good luck....just a note... since going on Singular his peakflows have been a lot more stable. One of his worst allergies is grass which sent him running indoors when he heard a lawnmower running outside. This summer he is cutting the lawn with no real changes in his peakflows. Again, Singular combined with discus Serevent has been a God send.
Renee